1. Field of the Invention
The present invention relates to a cell for the production of an antibody molecule such as an antibody useful for various diseases, a fragment of the antibody and a fusion protein having the Fc region of the antibody or the like, a method for producing an antibody composition using the cell, the antibody composition and use thereof.
2. Brief Description of the Background Art
Since antibodies have high binding activity, binding specificity and high stability in blood, their applications to diagnosis, prevention and treatment of various human diseases have been attempted [Monoclonal Antibodies: Principles and Applications, Wiley-Liss, Inc., Chapter 2.1 (1995)]. Also, production of a humanized antibody such as a human chimeric antibody or a human complementarity determining region (hereinafter referred to as “CDR”)-grafted antibody from an antibody derived from an animal other than human have been attempted by using genetic recombination techniques. The human chimeric antibody is an antibody in which its antibody variable region (hereinafter referred to as “V region”) is an antibody derived from an animal other than human and its constant region (hereinafter referred to as “C region”) is derived from a human antibody. The human CDR-grafted antibody is an antibody in which the CDR of a human antibody is replaced by CDR of an antibody derived from an animal other than human.
It has been revealed that five classes, namely IgM, IgD, IgG, IgA and IgE, are present in antibodies derived from mammals. Antibodies of human IgG class are mainly used for the diagnosis, prevention and treatment of various human diseases because they have functional characteristics such as long half-life in blood, various effector functions and the like [Monoclonal Antibodies: Principles and Applications, Wiley-Liss, Inc., Chapter 1 (1995)]. The human IgG class antibody is further classified into the following 4 subclasses: IgG1, IgG2, IgG3 and IgG4. A large number of studies have so far been conducted for antibody-dependent cell-mediated cytotoxic activity (hereinafter referred to as “ADCC activity”) and complement-dependent cytotoxic activity (hereinafter referred to as “CDC activity”) as effector functions of the IgG class antibody, and it has been reported that among antibodies of the human IgG class, the IgG1 subclass has the highest ADCC activity and CDC activity [Chemical Immunology, 65, 88 (1997)]. In view of the above, most of the anti-tumor humanized antibodies, including commercially available Rituxan and Herceptin, which require high effector functions for the expression of their effects, are antibodies of the human IgG1 subclass.
Expression of ADCC activity and CDC activity of the human IgG1 subclass antibodies requires binding of the Fc region of the antibody to an antibody receptor existing on the surface of an effector cell, such as a killer cell, a natural killer cell, an activated macrophage or the like (hereinafter referred to as “FcγR”) and various complement components are bound. Regarding the binding, it has been suggested that several amino acid residues in the hinge region and the second domain of C region (hereinafter referred to as “Cγ2 domain”) of the antibody are important [Eur. J. Immunol., 23, 1098 (1993), Immunology, 86, 319 (1995), Chemical Immunology, 65, 88 (1997)] and that a sugar chain binding to the Cγ2 domain [Chemical Immunology, 65, 88 (1997)] is also important.
Regarding the sugar chain, Boyd et al. have examined effects of a sugar chain on the ADCC activity and CDC activity by treating a human CDR-grafted antibody CAMPATH-1H (human IgG1 subclass) produced by a Chinese hamster ovary cell (CHO cell) or a mouse myeloma NSO cell (NSO cell) with various sugar hydrolyzing enzymes, and reported that elimination of the non-reducing end sialic acid did not have influence upon both activities, but the CDC activity alone was affected by further removal of galactose residue and about 50% of the activity was decreased, and that complete removal of the sugar chain caused disappearance of both activities [Molecular Immunol., 32, 1311 (1995)]. Also, Lifely et al. have analyzed the sugar chain bound to a human CDR-grafted antibody CAMPATH-1H (human IgG1 subclass) which was produced by CHO cell, NSO cell or rat myeloma YO cell, measured its ADCC activity, and reported that the CAMPATH-1H derived from YO cell showed the highest ADCC activity, suggesting that N-acetylglucosamine (hereinafter referred also to as “GlcNAc”) at the bisecting position is important for the activity [Glycobiology, 5, 813 (1995); WO 99/54342]. These reports indicate that the structure of the sugar chain plays an important role in the effector functions of human antibodies of IgG1 subclass and that it is possible to prepare an antibody having more higher effector function by changing the structure of the sugar chain. However, actually, structures of sugar chains are various and complex, and it cannot be said that an actual important structure for the effector function was identified.
Sugar chains of glycoproteins are roughly divided into two types, namely a sugar chain which binds to asparagine (N-glycoside-linked sugar chain) and a sugar chain which binds to other amino acid such as serine, threonine (O-glycoside-linked sugar chain), based on the binding form to the protein moiety. The N-glycoside-linked sugar chains have various structures [Biochemical Experimentation Method 23—Method for Studying Glycoprotein Sugar Chain (Gakujutsu Shuppan Center), edited by Reiko Takahashi (1989)], but it is known that they have a basic common core structure shown by the following structural formula (I). 
The sugar chain terminus which binds to asparagine is called a reducing end, and the opposite side is called a non-reducing end. It is known that the N-glycoside-linked sugar chain includes a high mannose type in which mannose alone binds to the non-reducing end of the core structure; a complex type in which the non-reducing end side of the core structure has at least one parallel branches of galactose-N-acetylglucosamine (hereinafter referred to as “Gal-GlcNAc”) and the non-reducing end side of Gal-GlcNAc has a structure of sialic acid, bisecting N-acetylglucosamine or the like; a hybrid type in which the non-reducing end side of the core structure has branches of both of the high mannose type and complex type; and the like.
In the Fc region of an antibody of an IgG type, two N-glycoside-linked sugar chain binding sites are present. In serum IgG, to the sugar chain binding site, generally, binds a complex type sugar chain having plural branches and in which addition of sialic acid or bisecting N-acetylglucosamine is low. It is known that there is variety in the manner and form in which addition of galactose is made to the non-reducing end of the complex type sugar chain and the addition of fucose to the N-acetylglucosamine in the reducing end [Leppanen, A, et al., Biochemistry, (1997) 36, 7026-7036, “in vitro Biosynthesis of a Decasacharide Prototype of Multiply Branched Polylactoaminoglycan Backbones”].
It has been considered that such a structure of a sugar chain is determined by sugar chain genes, namely a gene for a glycosyltransferase which synthesizes a sugar chain and a gene for a glycolytic enzyme which hydrolyzes the sugar chain.
Synthesis of an N-glycoside-linked sugar chain is described below.
Glycoproteins are modified with a sugar chain in the endoplasmic reticulum (hereinafter referred to as “ER”) lumen. During the biosynthesis step of the N-glycoside-linked sugar chain, a relatively large sugar chain is transferred to the polypeptide chain which is elongating in the ER lumen. In the transformation, the sugar chain is firstly added in succession to phosphate groups of a long chain lipid carrier comprising about 20 α-isoprene units, which is called dolichol phosphate (hereinafter referred also to as “P-Dol”). That is, N-acetylglucosamine is transferred to dolichol phosphate to thereby form GlcNAc-P-P-Dol and then one more GlcNAc is transferred to form GlcNAc-GlcNAc-P-P-Dol. Next, five mannoses (hereinafter mannose is also referred to as “Man”) are transferred to thereby form (Man)5-(GlcNAc)2-P-P-Dol and then four Man's and three glucoses (hereinafter glucose is also referred to as “Glc”) are transferred. Thus, a sugar chain precursor, (Glc)3-(Man)9-(GlcNAc)2-P-P-Dol, called core oligosaccharide is formed. The sugar chain precursor comprising 14 sugars is transferred as a mass to a polypeptide having an asparagine-X-serine or asparagine-X-threonine sequence in the ER lumen. In the reaction, dolichol pyrophosphate (P-P-Dol) bound to the core oligosaccharide is released but again becomes dolichol phosphate by hydrolysis with pyrophosphatase and is recycled. Trimming of the sugar chain immediately starts after the sugar chain binds to the polypeptide. That is, 3 Glc's and 1 or 2 Man's are eliminated on the ER, and it is known that α-1,2-glucosidase I, α-1,3-glucosidase II and α-1,2-mannosidase relates to the elimination.
The glycoprotein which was subjected to trimming on the ER is transferred to the Golgi body and are variously modified. In the cis part of the Golgi body, N-acetylglucosamine phosphotransferase which relates to addition of mannose phosphate, N-acetylglucosamine 1-phosphodiester α-N-acetylglucosamimidase and α-mannosidase I are present and reduce the Man residues to 5. In the medium part of the Golgi body, N-acetylglucosamine transferase I (GnTI) which relates to addition of the first outside GlcNAc of the complex type N-glycoside-linked sugar chain, α-mannosidase II which relates to elimination of 2 Man's, N-acetylglucosamine transferase II (GnTII) which relates to addition of the second GlcNAc from the outside and α-1,6-fucosyltransferase which relates to addition of fucose to the reducing end N-acetylglucosamine are present. In the trans part of the Golgi body, galactose transferase which relates to addition of galactose and sialyltransferase which relates to addition of sialic acid such as N-acetylneuraminic acid or the like are present. It is known that N-glycoside-linked sugar chain is formed by activities of these various enzymes.
In general, most of the humanized antibodies of which application to medicaments is in consideration are prepared using genetic recombination techniques and produced using Chinese hamster ovary tissue-derived CHO cell as the host cell. But as described above, since the sugar chain structure plays a remarkably important role in the effector function of antibodies and differences are observed in the sugar chain structure of glycoproteins expressed by host cells, development of a host cell which can be used for the production of an antibody having higher effector function is desired.
In order to modify the sugar chain structure of the produced glycoprotein, various methods have been attempted, such as 1) application of an inhibitor against an enzyme relating to the modification of a sugar chain, 2) selection of a mutant, 3) introduction of a gene encoding an enzyme relating to the modification of a sugar chain, and the like. Specific examples are described below.
Examples of an inhibitor against an enzyme relating to the modification of a sugar chain include tunicamycin which selectively inhibits formation of GlcNAc-P-P-Dol which is the first step of the formation of a core oligosaccharide which is a precursor of an N-glycoside-linked sugar chain, castanospermin and N-methyl-1-deoxynojirimycin which are inhibitors of glycosidase I, bromocondulitol which is an inhibitor of glycosidase II, 1-deoxynojirimycin and 1,4-dioxy-1,4-imino-D-mannitol which are inhibitors of mannosidase I, swainsonine which is an inhibitor of mannosidase II and the like. Examples of an inhibitor specific for a glycosyltransferase include deoxy derivatives of substrates against N-acetylglucosamine transferase V (GnTV) and the like [Glycobiology Series 2—Destiny of Sugar Chain in Cell (Kodan-sha Scientific), edited by Katsutaka Nagai, Senichiro Hakomori and Akira Kobata (1993)]. Also, it is known that 1-deoxynojirimycin inhibits synthesis of a complex type sugar chain and increases the ratio of high mannose type and hybrid type sugar chains. Actually, it has been reported that sugar chain structure of IgG was changed and properties such as antigen binding activity and the like was changed when the inhibitors were added to a medium [Molecular Immunol., 26, 1113 (1989)].
Mutants regarding the activity of an enzyme relating to the modification of a sugar chain are mainly selected and obtained as a lectin-resistant cell line. For example, CHO cell mutants having various sugar chain structures have been obtained as a lectin-resistant cell line using a lectin such as WGA (wheat-germ agglutinin derived from T. vulgaris), ConA (cocanavalin A derived from C. ensiformis), RIC (a toxin derived from R. communis), L-PHA (leucoagglutinin derived from P. vulgaris), LCA (lentil agglutinin derived from L. culinaris), PSA (pea lectin derived from P. sativum) or the like [Somatic Cell Mol. Genet., 12, 51 (1986)].
As an example of the modification of the sugar chain structure of a product obtained by introducing the gene of an enzyme relating to the modification of a sugar chain into a host cell, it has been reported that a protein in which a number of sialic acid is added to the non-reducing end of the sugar chain can be produced by introducing rat β-galactoside-α-2,6-sialyltransferase into CHO cell [J. Biol. Chem., 261, 13848 (1989)].
Also, it was confirmed that an H antigen (Fucα1-2Galβ1-) in which fucose (hereinafter also referred to as “Fuc”) was added to the non-reducing end of the sugar chain was expressed by introducing human β-galactoside-2-α-fucosyltransferase into mouse L cell [Science, 252, 1668 (1991)]. In addition, based on knowledge that addition of the bisecting-positioned N-acetylglucosamine of N-glycoside-linked sugar chain is important for the ADCC activity of antibody, Umana et al. have prepared CHO cell which expresses β-1,4-N-acetylglucosamine transferase III (GnTIII) and compared it with the parent cell line on the expresion of GnTIII. It was confirmed that express of GnTIII was not observed in the parent cell line of CHO cell [J. Biol. Chem., 261, 13370 (1984)], and that the antibody expressed using the produced GnTIII expressing CHO cell had ADCC activity 16 times higher than the antibody expressed using the parent cell line [Glycobiology, 5, 813 (1995): WO 99/54342]. At this time, Umana et al. have also produced CHO cell into which β-1,4-N-acetylglucosamine transferase V (GnTV) was introduced and reported that excess expression of GnTIII or GnTV shows toxicity for CHO cell.
Thus, in order to modify the sugar chain structure of the glycoprotein to be produced, control of the activity of the enzyme relating to the modification of a sugar chain in the host cell has been attempted, but actually, the structures of sugar chains are various and complex, and solution of the physiological roles of sugar chains would be insufficient, so that trial and error are repeated. Particularly, although it has been revealed little by little that the effector function of antibodies is greatly influenced by the sugar chain structure, a truly important sugar chain structure has not been specified yet. Accordingly, identification of a sugar chain which has influence upon the effector function of antibodies and development of a host cell to which such a sugar chain structure can be added are expected for developing medicaments.